[PATCH] D125717: [InstCombine] Optimize and of icmps with power-of-2 and contiguous masks

[John McIver via Phabricator via llvm-commits]

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All six reported failing tests (due to timeouts) are passing locally in my build/test environment.


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Fix capitzalation of function names containing ICMP


jmciver added a comment.

Based on functionality of the optimization I believe `foldLogOpOfMaskedICmps` to be a reasonable location. However, it maybe better to create a new function and call it from `InstCombinerImpl::foldAndOrOfICmps` based on the following.

The placement of the call to `foldLogOpOfMaskedICmps_AllZeros_BMask_NotMixed_and_NotAllOnes` in the function `foldLogOpOfMaskedICmps` breaks the consistency of the conditional testing based on the conjunction of left and right mask (see variable `Mask` line 586). It is possible to place calls to `foldLogOpOfMaskedICmps_AllZeros_BMask_NotMixed_and_NotAllOnes` in two locations in `foldLogOpOfMaskedICmps`:

- In function `foldLogOpOfMaskedIcmpsAsymmetric` called from conditional block `Mask == 0` (line 593)
- In conditional block `Mask & (Mask_NotAllZeros | BMask_NotAllOnes` (line 655)

I opted against this due to readability.

Thanks in advance for any feedback!


Add an instance combine optimization for expressions of the form:

(%arg u< C1 <https://reviews.llvm.org/C1>) & ((%arg & C2) != C2) -> %arg u< C2

Where C1 <https://reviews.llvm.org/C1> is a power-of-2 and C2 is a contiguous mask starting 1 bit below C1 <https://reviews.llvm.org/C1>.

This commit resolves GitHub missed-optimization issue #54856.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D125717

Files:
  llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
  llvm/test/Transforms/InstCombine/icmp-logical.ll

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